1. Field of the Invention
The present invention relates to an air intake duct, more particularly to an air intake duct for supplying air for a car engine.
2. Description of Related Art
Generally, air intake ducts for car engines use rubber or soft resin as material in order to meet the demand for light weight, vibration isolation and flexibility, and for more flexibility, bellows are formed partly in them. However, this kind of air intake ducts are inclined to be deformed inward by large negative pressure and cause problems like low engine power.
Therefore, reinforcements are conventionally arranged inside or outside around the duct. For example, Japanese utility-model laid-open publication 5-8167 discloses mounting metallic reinforcing rings on an internal surface of a duct with their spring. Also, Japanese patent laid-open publication No. 7-310869 discloses arranging plural protrusions sticking out of peaks of bellows, onto which reinforcing rings are mounted.
However, for both air intake ducts as mentioned above, it is necessary to mount by hand work reinforcing rings around inside or outside of the duct which is already molded, and the process is complicated.